А) (x+3y)/(3x-9y) + (3x-2y)/(2x-6y) = (x+3y)/[3(x-3y)] + (3x-2y)/[2(x-3y)] =
= [2(x+3y) + 3(3x-2y)] / [6(x-3y)] = (2x+6y+9x-6y) / [6(x-3y)] = 11x / [6(x-3y)]
б) (9d-10l)/(-90-45d) + 5z/(-10-5d) = (9d-10l+45z)/(-90-45d)
в) (9h-4t)/(-60j+36x) - (2s+10u)/(-90j+54x) = [3(9h-4t)-2(2s+10u)]/(-180j+108x)
= (27h-12t-4s-20u)/(-180j+108x)